The objective of this study is to investigate the relationship between home exposure to radon and lung cancer. This will be done through an analysis of 425 hist ologically confirmed cases of lung cancer and 425 age, sex and smoking matched controls. A similar case-control analysis will be conducted of 85 lung cancer cases among non-smokers, matched with 170 age and sex matched controls. The study will be conducted in five counties of Northwest New Jersey, an area with one of the geographically largest and intense radon releasing formations in the United States. Year-long radon measurements will be made and house construction features evaluated in all the homes lived in by study subjects over the period 5 to 30 years prior to case or control subject identification. The relative risk of radon exposure will be calculated using both stratified techniques and regression analyses. Additionally, a more sensitive analysts technique will be developed that takes advantage of information on individual smoking risks from large, general population studies. Information on other cancer risk factors in the diet, environment and work of each study subject will be obtained and considered in the analyses.